A thin film transistor (TFT) is a commonly used switching element in the display field. The TFT generally includes a gate electrode, an active layer, and a source electrode and a drain electrode which are electrically connected with the active layer. The active layer is usually made of a semiconductor material such as polycrystalline silicon or monocrystalline silicon.
An array substrate is an important component of a display device. The array substrate generally includes a display region and a non-display region. A plurality of TFTs arranged in a matrix is usually disposed in the display region. For instance, each TFT may be configured to control the display state of at least one pixel unit in the display region of the array substrate.